42 S. LOVEN, ON POURTALESIA, A GENUS OF ECHINOIDEA. 



overlooked, and have been mucli neglected, even in the latest works. Réaumur ^) was the 

 first who, early in the last century, observed them in a living Echinus and desci'ibed 

 some of their functions. But he was led to state that every single perforation, ritrowt, 

 of the ambiilacruin answered to a pedicel, and consequently that there were as many 

 pedicels as perforations. He also seems to have supposed that they are extended from 

 the interiör and drawn in again through the pores. Sixty years afterwards these errors 

 were corrected by J. A. Gyllenhahl, ") in the highl}^ remarkable paper in which he 

 deinonstrated the animal natui-e of the fossils then named »crystal äpples», »calcareous 

 nodules», or »Aetites», and ranged by Linn^eus among minerals, but which he proved 

 to be »petrified animals of the genus Echinus or its nearest allies». He described two 

 species, the Echinus pomum, now Sphajronis pomum, and Echinus aurantium, now 

 EchinosphfBra aurantium, both well-known forms of Cystoidea. Of the former he says: 



»Tentaculis procul dubio numerosissimis instructuin (iisdem lioet ipsis, prout mollioris substantise, adeoque 

 petrificationis iiicapacibus, non potuerint non oraniuo privata fuisse fossilia individua): Cutis enim undique 

 pertusa est poris minutissirais, ovbiculalis : Quorum geraini semper collooati sunt iiitra cancellum minutum; 

 insequilateri-angulatUHi; fundo convexum; plerumque oblougum et in singula extremitate pororum altero pertusumo. 



This he explains thus: 



))As »the teiitacles» are to be understood those soft and elastio fiilaments which in all other Echini are 

 attached to the surface of the test, each över a pair of small perforations. AU the species of Echinus hitherto 

 kuown possess cancelli on the surface of the test, corresponding with those described above in outline, in the 

 convexity of the bottom, and in the test being pievced, within every single cancellus, by two minute perfora- 

 tions, one at each of its ends, the cancellus comraonly being of an oval form. These two pores afiford the 

 communication between the internal parts and the tentacle, the basis of which occupies the entire cancellus, 

 and consequently covers both pores. In the new fossil species now described the cancelli are somewhat deeper 

 than in most other Echini, but in some of the irregular Echini I find those around the mouth to agree with 

 them in this respect also." 



And he adds, against Réaumur: 



»I have exaraiued Echini of dififerent species, such as they had been taken out of the sea and afterwards 

 dried, and these I have placed in warm water in order to make their substance swell and resumé its natural 

 shape, and thus I found that, instead of there being one tentacle to each pore, there is one tentacle correspon- 

 ding to each pair of pores.» . . . »It follows that the pores are twice as nuraerous as the tentacles». 



It will be noticed, that Gyllenhahl had an idea that in some of the Echini 

 irregulares of Linnjeus, the pedicellar pores near the oesophageal opening were somewhat 

 different from the rest. To the eminent Dane Otto Frederic Muller belongs, however, 

 the discovery, as early as in 1776, of the peculiar structure, in Spatangus purpureus, of 

 its circum-oral pedicels, of which, in the following year, he published a magnified figure. 



') Histoire de TAcadémie Royale des Sciences. Année MDCCXII. Aveo les mémoires de mathématique 

 et de physique pour la méme année. Paris 1714, 4:o, Mém. p. 1.36, pl. 8. 



^) Johan Abraham Gyllenhahl, in his twenty second year, oommunicated to the R. Swedish Academy of 

 Sciences the above quoted memoir: Beskrifning på de så kallade Crystall-äplen och kalkbollar, såsom 

 petreficerade djur af Echini genus, eller dess närmaste slägtingar. Kongl. Vetenskaps-Akademiens Hand- 

 lingar för är 1772, Vol. XXXIII, p. 2.H9. Translated into german in: Der Königl. Schwedischen Aka- 

 demie der Wissenschaften Abhandlungen aus der Naturlehre, Haushaltungskunst und Mechanik, auf das 

 Jahv 1772. Aus dem Schwedischen iibersetzt von^ Abraham Gotthelf Kästner. Bd. XXXIV, p. 231. 

 Leipzig 1776. — J. A. Gyllenhahl, elder brother of Leonard Gyllbnhaal, the eminent ^author of 

 »Insecta Suecica», was bom in 1750 and died in 1788, as Director of the Copper-mines at Åtvidaberg 

 in Ostro^othia. 



